Morphology and electrical properties of carbon coated LiFePO4 cathode materials

Core-shell LiFePO4@C composites were synthesized successfully from FePO4/C precursor using the polyvinyl alcohol (PVA) as the reducing agent, followed by a chemical vapor deposition (CVD) assisted solid-state reaction in the presence of Li2CO3. Some physical and chemical properties of the products were characterized by X-ray powder diffraction (XRD), Raman, SEM, TEM techniques. The effect of morphology and electrochemical properties of the composites were thoroughly investigated. XRD patterns showed that LiFePO4 has an order olivine structure with space group of Pnma. TEM micrographs exhibited that the LiFePO4 particles encapsulated with 3-nm thick carbon shells. The powders were homogeneous with grain size of about 0.8 μm. Compared with those synthesized by traditional organic carbon source mixed method, LiFePO4@C composite synthesized by CVD method exhibited better discharge capacity at initial 155.4 and 135.8 mAh g−1 at 0.1C and 1C rate, respectively. It is revealed that the carbon layer coated on the surface of LiFePO4 and the amorphous carbon wrapping and connecting the particles enhanced the electronic conductivity and rate performances of the cathode materials.